Bonebed

A bone bed is any geological stratum or deposit that contains bones of whatever kind. Inevitably, such deposits are sedimentary in nature. Not a formal term, it tends to be used more to describe especially dense collections such as Lagerstätte. It is also applied to brecciated and stalagmitic deposits on the floor of caves, which frequently contain osseous remains.

In a more restricted sense, the term is used to connote certain thin layers of bony fragments, which occur in well-defined geological strata. One of the best-known of these is the Ludlow Bone Bed, which is found at the base of the Downton Sandstone in the Upper Ludlow series. At Ludlow (England) itself, two such beds are actually known, separated by about 14 ft (4.3 m). of strata. Although quite thin, the Ludlow Bone Bed can be followed from that town into Gloucestershire, for a distance of 45 miles (72 km). It is almost completely made up of fragments of spines, teeth and scales of ganoid fish. Another well-known bed, formerly known as the Bristol or Lias Bone Bed, exists in the form of several thin layers of micaceous sandstone, with the remains of fish and saurians, which occur in the Rhaetic Black Paper Shales that lie above the Keuper marls, in the south-west of England. It is noteworthy that a similar bone bed has been traced on the same geological horizon in Brunswick, Hanover (Germany), in Franconia and in Tübingen (Germany). A bone bed has also been observed at the base of the Carboniferous limestone series, in certain parts of the south-west of England.

...
Wikipedia